This invention relates generally to the field of robotics and more specifically to a self-propelled climbing machine having endless-tracks. Such vehicles may be employed to perform remote operations in locations that are difficult for, or incompatible with, human presence or access. One example is a vehicle that can travel over a steel surface in a vertical, horizontal or upside-down configuration, such as on tanks, pipes, boiler walls or ship hulls, and also carry equipment to perform manufacture, maintenance or inspection functions.
There are many structures which require maintenance, repair, inspection or manufacturing operations that could be performed by a remote machine in a tele-operated or autonomous fashion. Numerous vehicles have been proposed to travel over inclined surfaces, and even operate upside down. These vehicles generally employ legs, wheels, or endless-tracks. Vehicles using endless-tracks provide several advantages, in particular the potential for a large area of contact between the vehicle and contact surface. Endless-tracks provide exceptional potential for large-area surface contact between the track-members (for example magnets) and the climbing-surface.
This invention concerns vehicles of the endless-track type with magnetic track-members incorporated in the endless-tracks. These vehicles are intended to operate on significant inclines, or upside down and/or on surfaces having, alone or in combination, concave, convex or irregular contours.
The endless-track type climbing vehicles available in previous technologies, may have, adhering track-members attached to the tracks and employ an endless-track of specific properties, to include very high tensile stiffness of the endless-track itself, in the axial direction of the track, but negligible stiffness in all transverse directions and negligible stiffness with respect to in bending. This creates a technological disadvantage in that the track in such cases is capable of supporting tensile forces, but, has only minimal stiffness in bending or in torsion for small angles it. Accordingly, it can support only negligible loads in any other direction, cannot support shear side-loads, and cannot support compressive loads.
To more closely examine circumstances under which this disadvantage becomes apparent, we note that for such a climbing vehicle to remain in equilibrium in any given position and orientation on a climbing-surface, forces affecting that equilibrium must be transferred from the climbing-surface to the vehicle. For a simple track type climbing vehicle, these forces are transferred from the track-members to the vehicle chassis through tensions in the endless-track. This would, ideally, allow the endless-track to accommodate irregular climbing-surface, but would concurrently result in localizing, on the outer adhering track-members, all of, or a majority of, the forces necessary to affect and maintain positional and orientational equilibrium with the climbing-surface.
The surface normal forces are a subset of the total forces that are required to maintain vehicle equilibrium on the climbing-surface. The surface normal forces are perpendicular to the climbing-surface and are required for equilibrium. To distribute this subset of forces in a manner intended to maintain equilibrium between the climbing vehicle and the climbing-CS, one might envision employment of a rigid guide section that slidably connects to the endless-track. But, this approach creates its own set of disadvantages in that it causes the surface normal forces to be localized on individual adhering track-members whenever and wherever climbing-surface irregularities are encountered.
The performance of an endless-track type climbing vehicle depends directly on the effective ability of the track, and accordingly, the track-members, to adhere to the climbing-surface. Numerous patents exist for climbing vehicles containing endless-tracks with adhering track-members incorporated into the tracks. One shortcoming of these previous technologies is their universal lack of a means to distribute the load among these adhering track-members in a manner that can accommodate a wide variety of surface geometries. Creation of such a load distribution means would significantly improve the performance of these climbing vehicles, and is, therefore, a desirable advancement in the art.
As is detailed below, previous technologies do not provide effective means to distribute the load among a plurality of adhering track-members.
Thus, an invention such as described herein, that distributes the forces required to maintain equilibrium between the vehicle and climbing-surface during operation among a plurality of adhering track-members, is novel to the state of art and is usefully and directly applicable to climbing vehicles having, or requiring, adhering track-members incorporated in endless-tracks. The herein taught art comprises a compliant suspension apparatus that distributes stiffness (and correspondingly the forces of equilibrium) relative to the plurality of adhering track-members.
The following discussion details and contrasts the instant art with illustrative examples of previous technologies and their associated shortcomings that the instant art overcomes.
U.S. Pat. No. 5,894,901, by Awamura, presents a traditional suspension system consisting of a plurality of press wheels equipped with elastic members (springs). These are capable of providing adjustment to the adhering members directed in to the climbing-surface only. The device provides, in contrast to the instant art, no means to compensate for, or to integrate, any other forces or balance adjustments. Although, as does the instant art, the Awamura et al. device includes magnets, an endless-track, and a suspension system, as designed, it only makes provision to adjustments necessary to push the magnets into contact with the climbing-surface. The device is equipped with auxiliary wheels, each wheel having a suspension supported by the vehicle body, pressing the wheel against the endless-track. These wheels are each supported by an elastic member in communication with the vehicle chassis. This is in contrast to the instant applicant's use of a compliant beam guide and support which automatically adjusts to balance the load carried and to maximize traction U.S. Pat. No. 5,435,405 by Schempf, et at teaches a reconfigurable mobile robot with magnetic tracks.
In contrast to the instant art, which uses permanently active magnets in the tracks, U.S. Pat. No. 5,435,405 by Schempf, et al teaches a magnetic system that can be activated and deactivated in the propulsion tracks. In further contrast, no guide, rigid or otherwise is mentioned with respect to the endless-track. Finally, unlike the instant art, the track appears to have no track-guide.
U.S. Pat. No. 4,789,037 by Kneebone uses two or more endless-tracks with plurality of permanent magnetic adhering members. Each adhering member comprises a permanent magnet sandwiched between magnetic metal plates. The magnet does not, itself, contact the climbing-surface, but contacts only these metal plates. As taught, it does allow pivotal rocking motion of track assemblies relative to the vehicle body, for negotiating uneven or curved surfaces, the track assemblies comprising, for each track unit, two laterally spaced chains, each forming an endless member. The device also uses a pump in the center of the body to apply additional upward or downward pressure to press the tracks onto the climbing-surface, and does teach a fan to create suction force normal to the climbing-surface. But the patent mentions no sort of trackguide, rigid or otherwise.
U.S. Pat. No. 5,884,642 by Broadbent teaches endless-tracks with plurality of magnetic sections, each tread using four rare earth magnetic segments, adjacent treads being oriented in opposing polarities. It does not, however, discuss any type of guide for the tracks, nor automatic balance control or adjustment.
U.S. Pat. No. 4,828,059, by Naito, et al. employs a track guide that is used only to engage and disengage track magnets from climbing-surfaces. Locations of loads carried by the Naito device are limited to remaining within the upper and lower planes of the endless propulsion tracks. It employs a plurality of permanent magnets on outer surface of crawler tracks and has a guidance device on crawler tracks for restraining and releasing crawler track from moving relative to crawler body in direction normal to traveling plane of magnets. It also includes a track control mechanism so designed such that the guidance device can restrain or release motion of the track to the main body in a direction normal to the surface. When this guide load is released, the load is essentially transferred in its entirety, to only the end magnets of the tracks.
U.S. Pat. No. 5,487,440, by Seemann presents a rigid guide, and a pair of parallel, endless-tracks equipped with suction cup feet These tracks slide along a grooved structure that allows for communication between a vacuum pump and those suction cups which are positioned for contact with the climbing-surface. It makes little or no provision for significant surface irregularities.
U.S. Pat. No. 6,672,413 B2 by Moore, et al. describes a remote controlled inspection vehicle utilizing magnetic adhesion to traverse non-horizontal, non-flat, ferromagnetic surfaces. Although this device employs magnets to adhere to the climbing-surface, no magnets are attached to, or guided by a track. The magnets are, rather, attached directly to the vehicle. The track comprises modules each of which contains a permanent magnet that the endless-track surrounds. These modules are so constructed as to pivot about longitudinal axes in an attempt to conform to pipes or other irregularities.